if i'm not pregnant, what could be going on??

- dd3 3 mths old, excl bf, no AF for me yet but I have had 3 'regular' clusters of several days with periody cramps

- had unprotected sex (i know, i know) 17 days ago

- have felt v. nauseous but also starving hungry the last 3-4 days (not actually thrown up, it comes and goes 'in waves')

- increased CM for 1-2 days at the end of last week, now nothing

- most importantly, a BFN yesterday evening, and a BFN this am (FMU) with ebay cheapie

I think i'm barking mad up the wrong tree to think i may be pg, but why am i getting these symptoms? (ok, not many symptoms i know). I know the only answer is to test in a week or so, but i just needed to write all this down, feel like i'm going a bit mad. Sorry to waffle on.